U.S. patent application number 14/376371 was filed with the patent office on 2015-02-05 for lens array and optical module including the same.
This patent application is currently assigned to ENPLAS CORPORATION. The applicant listed for this patent is ENPLAS CORPORATION. Invention is credited to Shimpei Morioka, Kazutaka Shibuya.
Application Number | 20150036985 14/376371 |
Document ID | / |
Family ID | 48947177 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150036985 |
Kind Code |
A1 |
Shibuya; Kazutaka ; et
al. |
February 5, 2015 |
LENS ARRAY AND OPTICAL MODULE INCLUDING THE SAME
Abstract
In an exemplary configuration, a lens array and a light module
using the same include a first lens surface 11 and a second lens
surface 12 formed into surface shapes such that by expanding the
luminous flux diameter of light as the light travels from the first
lens surface 11 toward the second lens surface 12, a light spot on
the second lens surface 12 is larger in diameter than a light spot
on the first lens surface 11, whereby the effects on optical
performance by foreign objects and scratches on the lens surface
can be mitigated, the criteria for the outward appearance of the
lens surface can therefore be mitigated and the yield rate
improved, and costs can be reduced.
Inventors: |
Shibuya; Kazutaka;
(Kawaguchi-shi, JP) ; Morioka; Shimpei;
(Kawaguchi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ENPLAS CORPORATION |
Kawaguchi-shi |
|
JP |
|
|
Assignee: |
ENPLAS CORPORATION
Kawaguchi-shi
JP
|
Family ID: |
48947177 |
Appl. No.: |
14/376371 |
Filed: |
December 14, 2012 |
PCT Filed: |
December 14, 2012 |
PCT NO: |
PCT/JP2012/082458 |
371 Date: |
August 1, 2014 |
Current U.S.
Class: |
385/93 |
Current CPC
Class: |
G02B 6/4286 20130101;
G02B 6/4214 20130101; G02B 6/425 20130101; G02B 6/4206
20130101 |
Class at
Publication: |
385/93 |
International
Class: |
G02B 6/42 20060101
G02B006/42 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2012 |
JP |
2012027188 |
Claims
1. A lens array that is disposed between a photoelectric conversion
device and an optical transmission body, the photoelectric
conversion device in which a plurality of photoelectric conversion
elements are disposed in an array, the lens array capable of
optically coupling the plurality of photoelectric conversion
elements and the optical transmission body, the lens array
comprising: a plurality of first lens faces that are disposed on a
first surface of a lens array main body on the photoelectric
conversion device side, such as to be arrayed in a predetermined
array direction corresponding with the plurality of photoelectric
conversion elements, and through which light of each photoelectric
conversion element that couples the plurality of photoelectric
conversion elements and the optical transmission body passes; and a
plurality of second lens faces that are disposed on a second
surface of the lens array main body on the optical transmission
body side, such as to be arrayed along the array direction, and
through which the light passes, wherein the first lens face or the
second lens face is formed having a face shape that increases the
light beam diameter of the light from the first lens face side
towards the second lens face side, thereby increasing a spot
diameter of the light on the second lens face to be larger than a
spot diameter of the light on the first lens face.
2. The lens array according to claim 1, wherein: the photoelectric
conversion element is a light-emitting element; and the first lens
face is formed into a convex lens face or a planar lens face that
converges the light emitted from the light-emitting element with a
weaker refractive power than that for collimation, or a concave
lens face that disperses the light of the light-emitting
element.
3. The lens array according to claim 1, wherein: the second surface
is disposed perpendicularly to the first surface; and a reflective
surface is disposed between the first lens faces and the second
lens faces, the reflective surface reflecting the light that has
entered from either the first lens face side or the second lens
face side towards the other of the first lens face side or the
second lens face side.
4. The lens array according to claim 3, wherein: the photoelectric
conversion device is that in which at least one light-receiving
element is disposed as the photoelectric conversion element, the
light-receiving element receiving monitor light for monitoring the
light emitted from at least one of the plurality of light-emitting
elements; and the lens array further includes at least one third
lens face that is disposed on the first surface and emits the
monitor light that has entered from the inner side of the lens
array main body towards the light-receiving element, and an optical
control unit that is disposed on an optical path between the
reflective surface and the second lens faces in the lens array main
body, on which the light of each light-emitting element that has
been reflected by the reflective surface towards the second lens
face side is incident, and that performs control such that the
incident light of each light-emitting element is reflected at a
predetermined reflection factor and advanced towards the third lens
face side, and transmitted at a predetermined transmission factor
and advanced towards the second lens face side, and at this time,
reflects the light of at least one of the plurality of
light-emitting elements as the monitor light.
5. The lens array according to claim 1, wherein the second surface
is disposed opposing the first surface; and the optical axis of the
first lens face and the optical axis of the second lens face are
disposed on a same line.
6. An optical module comprising: the lens array according to claim
1; and a photoelectric conversion device in which a plurality of
photoelectric conversion elements are disposed in an array.
7. The lens array according to claim 2, wherein: the second surface
is disposed perpendicularly to the first surface; and a reflective
surface is disposed between the first lens faces and the second
lens faces, the reflective surface reflecting the light that has
entered from either the first lens face side or the second lens
face side towards the other of the first lens face side or the
second lens face side.
8. The lens array according to claim 7, wherein: the photoelectric
conversion device is that in which at least one light-receiving
element is disposed as the photoelectric conversion element, the
light-receiving element receiving monitor light for monitoring the
light emitted from at least one of the plurality of light-emitting
elements; and the lens array further includes at least one third
lens face that is disposed on the first surface and emits the
monitor light that has entered from the inner side of the lens
array main body towards the light-receiving element, and an optical
control unit that is disposed on an optical path between the
reflective surface and the second lens faces in the lens array main
body, on which the light of each light-emitting element that has
been reflected by the reflective surface towards the second lens
face side is incident, and that performs control such that the
incident light of each light-emitting element is reflected at a
predetermined reflection factor and advanced towards the third lens
face side, and transmitted at a predetermined transmission factor
and advanced towards the second lens face side, and at this time,
reflects the light of at least one of the plurality of
light-emitting elements as the monitor light.
9. The lens array according to claim 2, wherein the second surface
is disposed opposing the first surface; and the optical axis of the
first lens face and the optical axis of the second lens face are
disposed on a same line.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lens array and an optical
module including the lens array. In particular, the present
invention relates to a lens array suitable for optically coupling a
photoelectric conversion element and an optical transmission body,
and an optical module including the lens array.
BACKGROUND ART
[0002] In recent years, the application of so-called optical
interconnection has become wide-spread as a technology for
transmitting signals at high speed within a system device, between
devices, or between optical modules. Here, optical interconnection
refers to a technology in which optical components are handled as
if they are electronic components, and are mounted on motherboards,
circuit boards, and the like used in personal computers, vehicles,
optical transceivers, and the like.
[0003] An optical module used in optical interconnection such as
this serves various purposes, such as internal connection for media
converters and switching hubs, and in-device and inter-device
component connection for optical transceivers, medical equipment,
testing devices, video systems, high-speed computer clusters, and
the like.
[0004] As an optical component applied to this type of optical
module, there is an increasing demand for a lens array in which a
plurality of lenses having a small diameter are disposed in
parallel, as a compactly structured component effective for
actualizing multichannel optical communication (refer to, for
example, Patent Literature 1).
[0005] Here, the lens array is conventionally configured such that
a photoelectric conversion device including a plurality of
light-emitting elements (such as a vertical cavity surface emitting
laser [VCSEL]) or light-receiving elements (such as photodetectors)
can be attached thereto, and a plurality of optical fibers serving
as an optical transmission body can be attached thereto.
[0006] In a state in which the lens array is disposed between the
photoelectric conversion device and the plurality of optical fibers
in this way, the lens array is capable of performing multichannel
optical transmission by optically coupling light emitted from each
light-emitting element of the photoelectric conversion device with
an end face of each optical fiber. The lens array is also capable
of performing multichannel optical reception by optically coupling
light emitted from the end face of each optical fiber with each
light-receiving element.
[0007] Here, the lens array of this type configures a sub-assembly
by being attached to a circuit board (chip-on-board [COB]) on which
photoelectric conversion elements (light-emitting elements and
light-receiving elements) serving as the photoelectric conversion
device are mounted.
[0008] A sub-assembly such as this configures a full assembly by an
optical connector housing the optical fibers, such as an MT
connector, being attached thereto. At this time, when an active
optical cable (AOC) is configured, the optical connector is
attached in a non-detachable state. On the other hand, when an
optical transceiver is configured, the optical connector is
attached in a detachable state. [0009] Patent Literature 1:
Japanese Patent Laid-open Publication No. 2004-198470
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0010] In the lens array that is in the sub-assembly state, the
lens faces on the photoelectric conversion device side are shielded
from the outside by the structure of the sub-assembly. Therefore,
adhesion of foreign matter, such as dust, and formation of
scratches on the lens faces rarely occur. Conversely, the lens
faces on the optical fiber side are not shielded from the outside
because the optical connector is not yet attached. Therefore,
adhesion of foreign matter and formation of scratches tend to occur
during attachment of the optical connector and the like.
[0011] Because multichannel optical communication is required to be
actualized using a compact lens array structure, the diameter
dimension of each lens face has certain restrictions. Therefore,
the area occupancy of foreign matter and scratches in relation to
the lens face becomes unavoidably high, as a matter of course.
[0012] As a result, a problem has occurred in the past in which
foreign matter and scratches on the lens faces cause significant
decrease in coupling efficiency between the photoelectric
conversion elements and the optical fibers.
[0013] Therefore, the present invention has been achieved in light
of the above-described issues. An object of the present invention
is to provide a lens array that is capable of reducing the effect
foreign matter and scratches on a lens face have on optical
performance, as well as relaxing outer appearance standards of the
lens face, improving yield, and reducing cost, and an optical
module including the lens array.
Means for Solving Problem
[0014] To achieve the above-described object, a lens array
according to a claim 1 of the present invention is a lens array
that is disposed between a photoelectric conversion device and an
optical transmission body, the photoelectric conversion device in
which a plurality of photoelectric conversion elements are disposed
in an array, the lens array capable of optically coupling the
plurality of photoelectric conversion elements and the optical
transmission body. The lens array includes: a plurality of first
lens faces that are disposed on a first surface of a lens array
main body on the photoelectric conversion device side, such as to
be arrayed in a predetermined array direction corresponding with
the plurality of photoelectric conversion elements, and through
which light of each photoelectric conversion element that couples
the plurality of photoelectric conversion elements and the optical
transmission body passes; and a plurality of second lens faces that
are disposed on a second surface of the lens array main body on the
optical transmission body side, such as to be arrayed along the
array direction, and through which the light passes. The first lens
face or the second lens face is formed having a face shape that
increases the light beam diameter of the light from the first lens
face side towards the second lens face side, thereby increasing a
spot diameter of the light on the second lens face to be larger
than a spot diameter of the light on the first lens face.
[0015] In the invention according to the claim 1, the area
occupancy of foreign matter/scratches in relation to a light spot
on the second lens face can be reduced. Therefore, although the
diameter dimension of the second lens face is restricted, the
effect foreign matter/scratches on the second lens face have on
coupling efficiency can be effectively reduced.
[0016] In addition, a lens array according to a claim 2 is the lens
array according to the claim 1 in which, further, the photoelectric
conversion element is a light-emitting element. The first lens face
is formed into a convex lens face or a planar lens face that
converges the light emitted from the light-emitting element with a
weaker refractive power than that for collimation, or a concave
lens face that disperses the light of the light-emitting
element.
[0017] In the invention according to the claim 2, when the light
from the light-emitting elements are coupled with the optical
transmission body, a light beam that widens in diameter from the
first lens face side towards the second lens face side can be
obtained with certainty. Therefore, the effect foreign
matter/scratches on the second lens face have on the coupling
efficiency of light to be coupled with the optical transmission
body can be reduced with certainty.
[0018] Furthermore, a lens array according to a claim 3 is the lens
array according to the claim 1 or 2 in which, further, the second
surface is disposed perpendicularly to the first surface. A
reflective surface is disposed between the first lens faces and the
second lens faces, the reflective surface reflecting the light that
has entered from either the first lens face side or the second lens
face side towards the other of the first lens face side or the
second lens face side.
[0019] In the invention according to the claim 3, the effect
foreign matter/scratches on the second lens face have on coupling
efficiency can be effectively reduced in a configuration suitable
for enabling the optical transmission body to extract light
(transmission light) emitted from light-emitting elements mounted
on a substrate from a direction parallel to the substrate, or
enabling a light-receiving element mounted on a substrate to
receive light (reception light) that is parallel to the substrate
and emitted from the optical transmission body.
[0020] Still further, a lens array according to a claim 4 is the
lens array according to the claim 3 in which, further, the
photoelectric conversion device is that in which at least one
light-receiving element is disposed as the photoelectric conversion
element, the light-receiving element receiving monitor light for
monitoring the light emitted from at least one of the plurality of
light-emitting elements. The lens array further includes: at least
one third lens face that is disposed on the first surface and emits
the monitor light that has entered from the inner side of the lens
array main body towards the light-receiving element; and an optical
control unit that is disposed on an optical path between the
reflective surface and the second lens faces in the lens array main
body, on which the light of each light-emitting element that has
been reflected by the reflective surface towards the second lens
face side is incident, and that performs control such that the
incident light of each light-emitting element is reflected at a
predetermined reflection factor and advanced towards the third lens
face side, and transmitted at a predetermined transmission factor
and advanced towards the second lens face side, and at this time,
reflects the light of at least one of the plurality of
light-emitting elements as the monitor light.
[0021] In the invention according to the claim 4, the effect
foreign matter/scratches on the second lens face have on coupling
efficiency can be effectively reduced in a configuration suitable
for adjustment of the output of light of the light-emitting
elements.
[0022] In addition, a lens array according to a claim 5 is the lens
array according to the claim 1 or 2 in which, further, the second
surface is disposed opposing the first surface. The optical axis of
the first lens face and the optical axis of the second lens face
are disposed on a same line.
[0023] In the invention according to the claim 5, the effect
foreign matter/scratches on the second lens face have on coupling
efficiency can be effectively reduced in a configuration in which
the second lens faces are disposed behind the first lens faces.
[0024] Furthermore, an optical module according to a claim 6
includes the lens array according to any one of the claims 1 to 5
and the photoelectric conversion device according to the claim 1,
2, or 4.
[0025] In the invention according to the claim 6, the effect
foreign matter/scratches on the second lens face have on coupling
efficiency can be effectively reduced.
Effect of the Invention
[0026] In the present invention, the effect foreign
matter/scratches on a lens face have on optical performance can be
reduced, and in addition, outer appearance standards of the lens
face can be relaxed, yield can be improved, and cost can be
reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIG. 1 An overall configuration diagram of a lens array and
an optical module including the lens array according to a first
embodiment of the present invention
[0028] FIG. 2 A bottom view of the lens array shown in FIG. 1
[0029] FIG. 3 A planar view of the lens array shown in FIG. 1
[0030] FIG. 4 A vertical cross-sectional view of a lens array in a
first variation example according to the first embodiment
[0031] FIG. 5 A vertical cross-sectional view of a lens array in a
second variation example according to the first embodiment
[0032] FIG. 6 A bottom view of FIG. 5
[0033] FIG. 7 A vertical cross-sectional view of a lens array in a
third variation example according to the first embodiment
[0034] FIG. 8 A bottom view of FIG. 7
[0035] FIG. 9 A planar view of FIG. 7
[0036] FIG. 10 A vertical cross-sectional view of a lens array in a
fourth variation example according to the first embodiment
[0037] FIG. 11 A vertical cross-sectional view of a lens array in a
fifth variation example according to the first embodiment
[0038] FIG. 12 An overall configuration diagram of a lens array and
an optical module including the lens array according to a second
embodiment of the present invention
[0039] FIG. 13 A bottom view of the lens array shown in FIG. 12
[0040] FIG. 14 A right-side view of the lens array shown in FIG.
12
[0041] FIG. 15 A vertical cross-sectional view of a lens array in a
first variation example according to the second embodiment
[0042] FIG. 16 A vertical cross-sectional view of a lens array in a
second variation example according to the second embodiment
[0043] FIG. 17 A bottom view of FIG. 16
[0044] FIG. 18 A vertical cross-sectional view of a lens array in a
third variation example according to the second embodiment
[0045] FIG. 19 A bottom view of FIG. 18
[0046] FIG. 20 A right-side view of FIG. 18
[0047] FIG. 21 A vertical cross-sectional view of a lens array in a
fourth variation example according to the second embodiment
[0048] FIG. 22 A vertical cross-sectional view of a lens array in a
fifth variation example according to the second embodiment
[0049] FIG. 23 An overall configuration diagram of a lens array and
an optical module including the lens array according to a third
embodiment of the present invention
[0050] FIG. 24 A bottom view of the lens array shown in FIG. 23
[0051] FIG. 25 A right-side view of the lens array shown in FIG.
23
[0052] FIG. 26 An enlarged vertical cross-sectional view of an
optical control unit
[0053] FIG. 27 An explanatory diagram for explaining a simulation
in Example 1
[0054] FIG. 28 A coupling efficiency characteristics graph
indicating the results of the simulation in Example 1
[0055] FIG. 29 A transmission factor characteristics graph
indicating the results of the simulation in Example 1
[0056] FIG. 30 An explanatory diagram for explaining a simulation
in Example 2
[0057] FIG. 31 A coupling efficiency characteristics graph
indicating the results of the simulation in Example 2
[0058] FIG. 32 A transmission factor characteristics graph
indicating the results of the simulation in Example 2
BEST MODE(S) FOR CARRYING OUT THE INVENTION
First Embodiment
[0059] A lens array and an optical module including the lens array
according to a first embodiment of the present invention will
hereinafter be described with reference to FIG. 1 to FIG. 11.
[0060] FIG. 1 is an overall configuration diagram of an overview of
a sub-assembly 1 serving as the optical module according to the
first embodiment, together with a vertical cross-sectional view of
a lens array 2 according to the first embodiment. In addition, FIG.
2 is a bottom view of the lens array 2 shown in FIG. 1.
Furthermore, FIG. 3 is a planar view of the lens array 2 shown in
FIG. 1.
[0061] As shown in FIG. 1, the lens array 2 according to the first
embodiment is disposed between a photoelectric conversion device 3
and optical fibers 5.
[0062] Here, the photoelectric conversion device 3 has a plurality
of light-emitting elements 7 on a surface of a semiconductor
substrate 6 facing the lens array 2, the light emitting-elements 7
emitting laser light La in a direction perpendicular to this
surface (upward direction in FIG. 1). The light-emitting elements 7
configure the above-described vertical cavity surface emitting
laser (VCSEL). In FIG. 1, the light-emitting elements 7 are formed
in an array along a direction perpendicular to the surface of the
paper on which FIG. 1 is printed. For example, the photoelectric
conversion device 3 such as this is disposed opposing the lens
array 2 in a state in which the semiconductor substrate 6 is in
contact with the lens array 2. In addition, for example, the
photoelectric conversion device 3 is attached to the lens array 2
by a known fixing means (not shown), such as a clamp spring,
thereby configuring the sub-assembly 1 together with the lens array
2.
[0063] In addition, the same number of optical fibers 5 according
to the first embodiment as the number of light-emitting elements 7
are arranged. The optical fibers 5 are disposed in an array along
the direction perpendicular to the surface of the paper on which
FIG. 1 is printed in FIG. 1, at the same pitch as the
light-emitting elements 7. The optical fibers 5 are, for example,
multi-mode optical fibers 5 that have the same dimensions as one
another. A portion of each optical fiber 5 on an end face 5a side
is held within a multi-core integrated optical connector 10, such
as the above-described MT connector. For example, the optical
fibers 5 such as these are attached to the lens array 2 by a known
fixing means (such as a clamp spring; not shown) in a state in
which the end face of the optical connector 10 on the lens array 2
side is in contact with the lens array 2.
[0064] The lens array 2 optically couples each light-emitting
element 7 with the end face 5a of each optical fiber 5 in a state
in which the lens array 2 is disposed between the photoelectric
conversion device 3 and the optical fibers 5 such as those
described above.
[0065] The lens array 2 will be described in further detail. As
shown in FIG. 1, the lens array 2 (lens array main body) is
composed of a light transmitting material (for example, a resin
material such as polyetherimide) and has a substantially planar
outer shape.
[0066] A lower end surface 2a of the lens array 2 such as that
described above functions as a first surface to which the
photoelectric conversion device 3 is attached. As shown in FIG. 1
and FIG. 2, a plurality (12 lens faces) of first lens faces 11
having a circular planar shape are formed on the lower end surface
2a. The number of first lens faces 11 is the same as the number of
light-emitting elements 7. Here, as shown in FIG. 1 and FIG. 2, a
section 2a' of the lower end surface 2a that has a substantially
rectangular planar shape and is in a predetermined area in the
center of the lower end surface 2a is formed into a recessed plane
(referred to, hereinafter, as a lens formation surface 2a') that
recesses further upwards than a peripheral section 2a'' with a
counterbore section 2A therebetween. The plurality of first lens
faces 11 are formed on the lens formation surface 2a' such as this.
However, the lens formation surface 2a' is formed in parallel with
the peripheral section 2a''. In addition, the first lens faces 11
are disposed in an array in a predetermined array direction (the
direction perpendicular to the surface of the paper on which FIG. 1
is printed in FIG. 1, and a vertical direction in FIG. 2)
corresponding with the light-emitting elements 7. Furthermore, the
first lens faces 11 are formed having the same dimensions as one
another, and are formed at the same pitch as the light-emitting
elements 7. The first lens faces 11 that are adjacent to each other
in the array direction may be formed in an adjacent state in which
the respective circumferential edge portions are in contact with
each other. In addition, as shown in FIG. 1, an optical axis OA(1)
of each first lens face 11 preferably matches a center axis of the
laser light La emitted from each light-emitting element 7
corresponding with each first lens face 11. More preferably, the
optical axis OA(1) of each first lens face 11 is perpendicular with
the lower end surface 2a.
[0067] On the other hand, an upper end surface 2b of the lens array
2 that opposes the lower end surface 2a functions as a second
surface to which the plurality of optical fibers 5 are attached. As
shown in FIG. 1 and FIG. 3, a plurality of second lens faces 12
having a circular planar shape are formed on the upper end surface
2b. The number of second lens faces 12 is the same as the number of
first lens faces 11. Here, as shown in FIG. 1 and FIG. 3, a section
2b' of the upper end surface 2b that has a substantially
rectangular planar shape and is in a predetermined area in the
center of the upper end surface 2b is formed into a recessed plane
(referred to, hereinafter, as a lens formation surface 2b') that
recesses further downwards in FIG. 1 than a peripheral section 2b''
that surrounds the section 2b' with a counterbore section 2B
therebetween. The plurality of second lens faces 12 are formed on
the lens formation surface 2b' such as this. However, the lens
formation surface 2b' is formed in parallel with the peripheral
section 2b''. In addition, the plurality of second lens faces 12
are disposed in an array in the same direction as the array
direction of the end faces 5a of the optical fibers 5, or in other
words, the array direction of the first lens faces 11. Furthermore,
the second lens faces 12 are formed having the same dimensions as
one another, and are formed at the same pitch as the first lens
faces 11. The second lens faces 12 that are adjacent to each other
in the array direction may be formed in an adjacent state in which
the respective circumferential edge portions are in contact with
each other. In addition, an optical axis OA(2) of each second lens
face 12 is preferably positioned on the same axis as the center
axis of the end face 5a of each optical fiber 5 corresponding with
each second lens face 12. More preferably, the optical axis OA(2)
of each second lens face 12 is perpendicular with the upper end
surface 2b. Furthermore, the optical axis OA(2) of each second lens
face 12 is disposed on the same line as the optical axis OA(1) of
each first lens face 11 corresponding with each second lens face
12.
[0068] According to the first embodiment, each lens face 11
increases the light beam diameter of the laser light La from the
first lens face 11 side towards the second lens face 12 side,
thereby forming the planar shape of the spot diameter (diameter of
the outer circumferential edge of the projection area of the laser
light La; the same applies hereafter) of the laser light La on the
second lens face 12 to be larger than the spot diameter of the
laser light La on the first lens face 11. Specifically, each first
lens face 11 is formed into a convex lens face having a weaker
refractive power (in other words, a greater radius of curvature)
than a collimate lens face. The convex lens face may be spherical
or aspherical. However, the face shape of the first lens face 11 is
designed to allow the spot (projection area) of the laser light La
on the second lens face 12 to fit within the effective diameter of
the second lens face 12. In designing such a face shape, it goes
without saying that the distance between the first lens face 11 and
the second lens face 12 (lens thickness), the distance between the
light-emitting element 7 and the first lens face 11, the beam
dispersion angle (in other words, NA) of the laser light La emitted
from the light-emitting element 7, and the like are taken into
consideration, in addition to the effective diameter of the second
lens face 12.
[0069] As shown in FIG. 1, the laser light La emitted from each
light-emitting element 7 corresponding with each first lens face 11
is incident on each first lens face 11 such as this. Each first
lens face 11 advances the incident laser light La of each
light-emitting element 7 into the lens array 2. At this time, the
laser light La of each light-emitting element 7 is converged with a
weaker refractive power than that for collimation because of the
face shape of each first lens face 11. As a result, the light beam
diameter of the laser light La of each light-emitting element 7
increases from the first lens face 11 side towards the second lens
face 12 side.
[0070] On the other hand, the second lens face 12 is formed into a
spherical or aspherical convex lens face. As shown in FIG. 1, the
laser light La of each light-emitting element that has been
converged by each first lens face 11 corresponding with each second
lens face 12 is incident on each second lens face 12. At this time,
the spot diameter of the laser light La on the second lens face 12
is larger than the spot diameter of the laser light La on the first
lens face 11. Each second lens face 12 then converges the incident
laser light La of each light-emitting element 7 and emits the laser
light La towards the end face 5a of each optical fiber 5
corresponding with each second lens face 12.
[0071] In this way, each light-emitting element 7 and the end face
5a of each optical fiber 5 are optically coupled by first lens face
11 and the second lens face 12.
[0072] In the above-described configuration, the area occupancy of
foreign matter/scratches in relation to the light spot on the
second lens face 12 can be reduced in a configuration in which the
second lens face 12 is disposed behind the first lens face 11. As a
result, while the diameter dimension of the second lens face 12 is
restricted, the effect foreign matter/scratches on the second lens
face 12 has on coupling efficiency can be effectively reduced.
[0073] In addition, as shown in FIG. 2, a pair of through holes 14
that pass through the lower end surface 2a and the upper end
surface 2b are bored in the peripheral section 2a'' of the lower
end surface 2a, on both outer side positions in relation to the
lens formation surface 2a' in the array direction of the first lens
faces 11. The through holes 14 are used for mechanical positioning
when the photoelectric conversion device 3 and the optical fibers 5
are attached, as a result of pins (not shown) respectively provided
on the photoelectric conversion device 3 and the optical connector
10 being inserted therein. However, pins may be provided instead of
the through holes 14, and through holes or bottomed-holes may be
provided on the photoelectric conversion device 3 side and the
optical connector 10 side.
[0074] According to the first embodiment, various variation
examples such as those below may be applied to the basic
configuration shown in FIG. 1 to FIG. 3.
First Variation Example
[0075] For example, as shown in FIG. 4, each first lens face 11 may
be a spherical or aspherical concave lens face. In this instance,
the laser light La of each light-emitting element 7 that has
entered each first lens face 11 is dispersed by each first lens
face 11. As a result, the light beam diameter increases as the
laser light La of each light-emitting element 7 advances towards
the second lens face 12. Therefore, in a manner similar to that in
the basic configuration, the spot diameter of the laser light La on
each second lens face 12 can be made larger than the spot diameter
of the laser light La on each first lens face 11 in the first
variation example as well. As a result, the effect foreign
matter/scratches on the second lens face 12 has on coupling
efficiency can be effectively reduced.
Second Variation Example
[0076] In addition, as shown in the vertical cross-sectional view
in FIG. 5 and the bottom view in FIG. 6, each first lens face 11
may be formed into a planar lens face. In this instance, the first
lens faces 11 may not be able to be differentiated in terms of
outer appearance. However, in terms of design, the first lens faces
11 are clearly differentiated by respective areas (broken line
sections in FIG. 6).
[0077] In the second variation example, the laser light La of each
light-emitting element 7 that has entered each first lens face 11
is converged by each first lens face 11 with a weaker refractive
power than that for collimation. As a result, the light beam
diameter is increased as the laser light La of each light-emitting
element 7 advances towards the second lens face 12 side. Therefore,
working effects similar to those of the basic configuration can be
achieved in the second variation example as well.
Third Variation Example
[0078] In addition, as shown in the vertical cross-sectional view
in FIG. 7, the bottom view in FIG. 8, and the planar view in FIG.
9, the number of first lens faces 11 and the number of second lens
faces 12 in the basic configuration may be increased. Specifically,
in the third variation example, two rows of 12 first lens faces 11
and two rows of 12 second lens faces 12 are disposed, thereby
actualizing 24-channel optical communication.
Fourth Variation Example
[0079] Furthermore, as shown in FIG. 10, the number of first lens
faces 11 and the number of second lens faces 12 in the first
variation example may be increased to two rows of 12 first lens
faces 11 and two rows of 12 second lens faces 12 (24 each).
Fifth Variation Example
[0080] Still further, as shown in FIG. 11, the number of first lens
faces 11 and the number of second lens faces 12 in the second
variation example may be increased to two rows of 12 first lens
faces 11 and two rows of 12 second lens faces 12.
Second Embodiment
[0081] Next, a lens array and an optical module including the lens
array according to a second embodiment of the present invention
will be described with reference to FIG. 12 to FIG. 22.
[0082] Sections of which the basic configuration is the same or
similar to that according to the first embodiment are described
using the same reference numbers.
[0083] FIG. 12 is an overall configuration diagram of an overview
of a sub-assembly 21 according to the second embodiment, together
with a vertical cross-sectional view of a lens array 22. In
addition, FIG. 13 is a bottom view of the lens array 22 shown in
FIG. 12. Furthermore, FIG. 14 is a right-side view of the lens
array 22 shown in FIG. 12.
[0084] As shown in FIG. 12, the lens array 22 according to the
second embodiment is disposed between the photoelectric conversion
device 3 and the optical fibers 5 in a manner similar to that
according to the first embodiment. In addition, the basic
configurations of the photoelectric conversion device 3 and the
optical fibers 5 are similar to those according to the first
embodiment.
[0085] However, the sub-assembly 21 according to the second
embodiment is configured so that the laser light La emitted from
each light-emitting element 7 mounted on the substrate 6 is
extracted from a direction parallel to the substrate 6 at the end
face 5a of each optical fiber 5.
[0086] A specific configuration is as follows.
[0087] In other words, as shown in FIG. 12, the lens array 22 (lens
array main body) is composed of a light-transmitting material (for
example, a resin material such as polyetherimide) and has a
substantially rectangular parallelepiped outer shape.
[0088] A lower end surface 22a of the lens array 22 such as this
functions as a first surface to which the photoelectric conversion
device 3 is attached. As shown in FIG. 12 and FIG. 13, a plurality
(12 lens faces) of first lens faces 11 having a circular planar
shape are disposed in an array along the light-emitting elements 7
on the lower end surface 2a. The number of first lens faces 11 is
the same as the number of light-emitting elements 7. In a manner
similar to that according to the first embodiment, the first lens
faces 11 are formed on a lens formation surface 22a' that is a
recessed plane formed in a predetermined area in the center of the
lower end surface 22a.
[0089] On the other hand, according to the second embodiment, a
right end surface 22c of the lens array 22 that is disposed
perpendicularly to the lower end surface 22a functions as a second
surface to which the plurality of optical fibers 5 are attached. In
other words, as shown in FIG. 12 and FIG. 14, a plurality of second
lens faces 12 having a circular planar shape are formed on the
upper end surface 2b. The number of second lens faces 12 is the
same as the number of first lens faces 11. In a manner similar to
that according to the first embodiment, the second lens faces 12
are formed on a lens formation surface 22c' that is a recessed
plane formed in a predetermined area in the center of the right end
surface 22c.
[0090] Furthermore, as shown in FIG. 12, a reflective surface 23 is
formed in a recessing manner on an upper end surface 22b of the
lens array 22. The reflective surface 23 is composed of a sloped
plane that has a predetermined slope angle in relation to the lower
end surface 22a and the right end surface 22c. The slope angle of
the reflective surface 23 may be 45.degree. in relation to both the
lower end surface 22a and the right end surface 22c.
[0091] In a manner similar to that in the basic configuration
according to the first embodiment, each first lens face 11 is
formed into a convex lens face that increases the light beam
diameter of the laser light La from the first lens face 11 side
towards the second lens face 12 side, thereby increasing the spot
diameter of the laser light La on the second lens face 12 to be
larger than the spot diameter of the laser light La on the first
lens face 11.
[0092] In the above-described configuration according to the second
embodiment, as shown in FIG. 12, the laser light La of each
light-emitting element 7 that is emitted upwards from each
light-emitting element 7 is incident on each first lens face 11. As
a result of the face shape of each first lens face 11, each first
lens face 11 converges the laser light La of each light-emitting
element 7 with a weaker refractive power than that for collimation.
Therefore, the light beam diameter of the laser light La of each
light-emitting element 7 is increased from the first lens face 11
side towards the second lens face 12 side. After the laser light La
of each light-emitting element 7 is projected with a large spot
diameter within the effective diameter of each second lens face 12,
the laser light La is then emitted from each second lens face 12
towards the end face 5a of each optical fiber 5. In the process, as
shown in FIG. 12, the laser light La of each light-emitting element
7 that has been converged by each first lens face 11 is incident on
the reflective surface 23 at an angle of incidence that is greater
than the critical angle from below. The reflective surface 23 then
totally reflects the incident laser light La of the light-emitting
element 7 towards each second lens face 12.
[0093] According to the second embodiment, the effect foreign
matter/scratches on the second lens face 12 has on coupling
efficiency can be effectively reduced in a configuration suitable
for extracting the laser light La emitted from the light-emitting
elements 7 mounted on the substrate 6 from a direction parallel to
the substrate 6 at the end faces 5a of the optical fibers 5.
[0094] According to the second embodiment, as shown in FIG. 12 to
FIG. 14, a pin 14' is erected on the right end surface 22c side for
mechanical positioning of the optical fibers 5. The pin 14' is
inserted into a through hole or a bottomed-hole (not shown)
provided on the connector 10 side, and is thereby used to position
the optical fibers 5.
[0095] In a manner similar to that according to the first
embodiment, according to the second embodiment as well, various
variation examples such as those below may be applied to the basic
configuration shown in FIG. 12 to FIG. 14.
First Variation Example
[0096] For example, as shown in FIG. 15, each first lens face 11
may be formed into a spherical or aspherical convex lens face.
Second Variation Example
[0097] In addition, as shown in the vertical cross-sectional view
in FIG. 16 and the bottom view in FIG. 17, each first lens face 11
may be formed into a planar lens face.
Third Variation Example
[0098] Furthermore, as shown in the vertical cross-sectional view
in FIG. 18, the bottom view in FIG. 19, and the right-side view in
FIG. 20, the number of first lens faces 11 and the number of second
lens faces 12 in the basic configuration may be increased to two
rows of 12 first lens faces 11 and two rows of 12 second lens faces
12 (24 each).
Fourth Variation Example
[0099] Still further, as shown in FIG. 21, the number of first lens
faces 11 and the number of second lens faces 12 in the first
variation example may be increased to two rows of 12 first lens
faces 11 and two rows of 12 second lens faces 12.
Fifth Variation Example
[0100] In addition, as shown in FIG. 22, the number of first lens
faces 11 and the number of second lens faces 12 in the second
variation example may be increased to two rows of 12 first lens
faces 11 and two rows of 12 second lens faces 12.
Third Embodiment
[0101] Next, a lens array and an optical module including the lens
array according to a third embodiment of the present invention will
be described with reference to FIG. 23 to FIG. 26.
[0102] Sections of which the basic configuration is the same or
similar to that according to the first embodiment are described
using the same reference numbers.
[0103] FIG. 23 is an overall configuration diagram of an overview
of a sub-assembly 31 according to the third embodiment, together
with a vertical cross-sectional view of a lens array 32. In
addition, FIG. 24 is a bottom view of the lens array 32 shown in
FIG. 23. Furthermore, FIG. 25 is a right-side view of the lens
array 32 shown in FIG. 23.
[0104] As shown in FIG. 23, the lens array 32 according to the
third embodiment is disposed between the photoelectric conversion
device 3 and the optical fibers 5 in a manner similar to that
according to the first embodiment and the second embodiment. In
addition, the basic configuration of the optical fibers 5 is
similar to that according to the first embodiment and the second
embodiment.
[0105] In a manner similar to that according to the second
embodiment, the sub-assembly 31 according to the third embodiment
is configured so that the laser light La emitted from each
light-emitting element 7 mounted on the substrate 6 is extracted
from a direction parallel to the substrate 6 at the end face 5a of
each optical fiber 5.
[0106] However, unlike those according to the first embodiment and
the second embodiment, the sub-assembly 31 according to the third
embodiment is configured to enable feedback of some of the laser
light La emitted from the light-emitting elements 7 and adjustment
of the output of the laser light La (such as intensity and amount
of light.
[0107] A specific configuration is as follows.
[0108] In other words, as shown in FIG. 23, the photoelectric
conversion device 3 has a plurality of light-receiving elements 8
on the surface of the semiconductor substrate 6 on the lens array
32 side, in positions to the right side of the light-emitting
elements 7 in FIG. 23. The light-receiving elements 8 receive
monitor light M for monitoring the output of the laser light L
emitted from the light-emitting elements 7. The number of
light-receiving elements 8 is the same as the number of
light-emitting elements 7. The light-receiving elements 8 may be
photodetectors. Furthermore, electronic components (not shown),
such as a control circuit that controls the output of the laser
light La emitted from the light-emitting elements 7 based on the
intensity and the amount of light of the monitor light M received
by the light-receiving elements 8, are mounted on the surface of
the semiconductor substrate 6 on the lens array 32 side. The
electronic components are electrically connected to the
light-emitting elements 7 and the light-receiving elements 8 by
wiring.
[0109] In addition, as shown in FIG. 23, the lens array 32 has a
lens array main body 34 that is composed of a light-transmitting
material and has a substantially rectangular parallelepiped outer
shape.
[0110] As shown in FIG. 23 and FIG. 24, the lens array main body 34
has a plurality (12 lens faces) of first lens faces 11 having a
circular planar shape on a lower end surface 34a that serves as a
first surface to which the photoelectric conversion device 3 is
attached. The number of first lens faces 11 is the same as the
number of light-emitting elements 7. In a manner similar to that
according to the first embodiment, the first lens faces 11 are
formed in an array along the light-emitting elements 7, on a lens
formation surface 34a' that is a recessed plane formed in a
predetermined area in the center of the lower end surface 34a.
[0111] In addition, as shown in FIG. 23 and FIG. 25, the lens array
main body 34 has a plurality of second lens faces 12 on a right end
surface 34c in FIG. 1 that serves as a second surface to which the
optical fibers 5 are attached. The number of second lens faces 12
is the same as the number of first lens faces 11. In a manner
similar to that according to the first embodiment, the second lens
faces 12 are formed in an array on a lens formation surface 34c'
that is a recessed plane formed in a predetermined area in the
center of the right end surface 34c.
[0112] Furthermore, as shown in FIG. 23, in a manner similar to
that according to the first embodiment, a reflective surface 23 is
formed in a recessing manner on an upper end surface 34b of the
lens array main body 34. The reflective surface 23 is composed of a
sloped plane that has a predetermined slope angle in relation to
the lower end surface 34a and the right end surface 34c. The slope
angle of the reflective surface 23 may be 45.degree. in relation to
both the lower end surface 34a and the right end surface 34c.
[0113] Still further, as shown in FIG. 23 and FIG. 24, third lens
faces 13 are formed in the lens formation area 34a' of the lower
end surface 34a in a position near the right-hand side of the first
lens faces 11. The number of third lens faces 13 is the same as the
number of the light-receiving elements 8 (according to the third
embodiment, the number of third lens faces 13 is also the same as
the number of light-emitting elements 7, the number of optical
fibers 5, the number of first lens faces 11, and the number of
second lens faces 12). The third lens faces 13 are disposed in an
array in a predetermined array direction corresponding with the
light-receiving elements 8, or in other words, the same direction
as the lens array direction. In addition, the third lens faces 13
are formed at the same pitch as the light-receiving elements 8. An
optical axis OA(3) of each third lens face 13 preferably matches
the center axis of a light-receiving surface of each
light-receiving element 8 corresponding with each third lens face
13.
[0114] In addition, as shown in FIG. 23, an optical control unit 4
is disposed on the optical path between the reflective surface 23
and the second lens faces 12.
[0115] The optical control unit 4 is configured by a prism
placement recessing section 41, a prism 42, a
reflective/transmissive layer 43, and a filler material 44. The
prism placement recessing section 41 is formed in a recessing
manner on the upper end surface 34b of the lens array main body 34,
in a position on the right of the reflective surface 23 that is
also a position opposing the third lens faces 13. The prism 42 is
placed within the recessing section 41. The reflective/transmissive
layer 43 is disposed on the prism 42. The filler material 44 fills
the area between the prism placement recessing section 41 and the
prism 42.
[0116] More specifically, as shown in FIG. 23, a left inner surface
41a and a right inner surface 41b of the prism placement recessing
section 41 are formed parallel to the lens formation surface 34c'
of the right end surface 34c.
[0117] In addition, as shown in FIG. 23, the prism 42 has an
incident surface 42a for the laser light La of each light-emitting
element 7 in a position facing the left inner surface 41a of the
prism placement recessing section 41 from the right side. As shown
in FIG. 23, the incident surface 42a is formed into a sloped
surface such that a lower end portion thereof is positioned further
to the right side than an upper end portion thereof. The slope
angle of the incident surface 42a is preferably 45.degree. in the
clockwise direction in FIG. 23, with reference to the lower end
surface 34a. In addition, as shown in FIG. 23, the prism 42 has an
outgoing surface 42b for the laser light La of each light-emitting
element 7 in a position opposing the incident surface 42a from the
right side. As shown in FIG. 23, the outgoing surface 42b opposes
the right inner surface 41b of the prism placement recessing
section 41 in a parallel manner, with a predetermined space
therebetween. However, a portion of the right end surface of the
prism 42 that is above the outgoing surface 42b may be placed in
close contact with the right inner surface 41b of the prism
placement recessing section 41. Furthermore, as shown in FIG. 23, a
plate-shaped shoulder section 45 is integrally formed in an upper
portion of the prism 42. The shoulder section 45 is provided for
convenience, such as in handling the compact prism 42 (for
placement into the prism placement recessing section 41) and to
prevent infiltration of foreign matter (such as dust) into the
prism placement recessing section 41. Furthermore, as shown in FIG.
23, a bottom surface 42c of the prism 42 connected between the
lower end portion of the incident surface 42a and the lower end
portion of the outgoing surface 42b is disposed in a position above
an inner bottom surface 41c of the prism placement recessing
section 41.
[0118] Furthermore, as shown in FIG. 23, the above-described
reflective/transmissive layer 43 is on the incident surface 42a of
the prism 42. The reflective/transmissive layer 43 may be formed by
a single-layer film composed of a single metal, such as Ni, Cr, or
Al. Alternatively, the reflective/transmissive layer 43 may be
formed by a dielectric multilayer film obtained by a plurality of
dielectrics having differing dielectric constants (such as
TiO.sub.2 and SiO.sub.2) being alternately stacked. Moreover, the
reflective/transmissive layer 43 may be formed by the
above-described metal single-layer film or dielectric multilayer
film being coated on the incident surface 42a. A known coating
technique, such as Inconel deposition, can be used for coating.
When a coating technique such as this is used, the
reflective/transmissive layer 43 can be formed into a very thin
thickness (such as 1 .mu.m or less).
[0119] Still further, as shown in FIG. 23, the above-described
filler material 44 completely fills the space between the left
inner surface 41a of the prism placement recessing section 41 and
the reflective/transmissive layer 43, and the space between the
right inner surface 41b of the prism placement recessing section 41
and the outgoing surface 42b of the prism 42. In addition, the
filler material 44 is composed of an adhesive, such as an acrylate
adhesive or an epoxy adhesive serving as an ultraviolet-curable
resin. The prism 42 is stably adhered within the prism placement
recessing section 41.
[0120] In addition, the lens array main body 34, the prism 42, and
the filler material 44 are formed such that the difference in
refraction index therebetween is a predetermined value (such as
0.05) or less. For example, when the lens array main body 34 and
the prism 42 are composed of Ultem (registered trademark),
manufactured by SABIC, as the polyetherimide, the refractive index
of the lens array main body 34 and the prism 42 is 1.64 (difference
in refractive index 0.00) for light having a wavelength of 850 nm.
As the corresponding filler material 44, LPC1101 manufactured by
Mitsubishi Gas Chemical Company, Inc. can be used. The refractive
index of LPC1101 is 1.66 for light having a wavelength of 850 nm,
calculated based on the refractive index and the Abbe number in
relation to the d line of values published by the manufacturer.
[0121] Furthermore, in a manner similar to that in the basic
configuration according to the first embodiment, each lens face 11
is formed into a convex lens face that increases the light beam
diameter of the laser light La from the first lens face 11 side
towards the second lens face 12 side, thereby increasing the spot
diameter of the laser light La on the second lens face 12 to be
larger than the spot diameter of the laser light La on the first
lens face 11.
[0122] In the above-described configuration according to the third
embodiment, as shown in FIG. 23, first, the laser light La of each
light-emitting element 7 that is emitted upwards from each
light-emitting element 7 is incident on each first lens face 11. As
a result of the face shape of each first lens face 11, each first
lens face 11 converges the laser light La of each light-emitting
element 7 with a weaker refractive power than that for collimation.
Therefore, the light beam diameter of the laser light La of each
light-emitting element 7 is increased from the first lens face 11
side towards the advancing direction.
[0123] Next, the laser light La that has been converged by each
first lens face 11 is incident on the reflective surface 23 at an
angle of incidence that is greater than the critical angle. The
reflective surface 23 totally reflects the incident laser light La
of each light-emitting element 7 towards the optical control unit
4.
[0124] Next, the laser light La of each light-emitting element 7
that has been totally reflected by the reflective surface 23 is
incident on the optical control unit 4, while increasing in light
beam diameter as the laser light La advances. At this time, because
the difference in refractive index between the lens array main body
34 and the filler material 44 is small, as shown in FIG. 26,
refraction of the laser light La when entering the border between
the left inner surface 41a of the and the filler material 44 in the
prism placement recessing section 41 does not occur.
[0125] Next, the laser light La of each light-emitting element 7
that has advanced through the filler material 44 is incident on the
reflective/transmissive layer 43, while increasing in light beam
diameter as the laser light La advances. The
reflective/transmissive layer 43 then reflects the laser light La
of each light-emitting element 7 that has entered in this way
towards the third lens face 13 side at a predetermined reflection
factor. In addition, the reflective/transmissive layer 43 transmits
the laser light La of each light-emitting element 7 that has
entered in this way towards the incident surface 42a side of the
prism 42. As the reflection factor and the transmission factor of
the reflective/transmissive layer 43, desired values can be set
depending on the material, thickness, and the like of the
reflective/transmissive layer 43, to the extent that an amount of
monitor light M sufficient for monitoring the output of the laser
light La can be obtained. As shown in FIG. 23, during reflection or
transmission such as this, the reflective/transmissive layer 43
reflects some (light amounting to the reflection factor) of the
laser light La of each light-emitting element 7 that has entered
the reflective/transmissive layer 43 as the monitor light M of each
light-emitting element 7 corresponding with each light-emitting
element 7, towards the third lens face 13 corresponding with each
beam of monitor light M.
[0126] Furthermore, the monitor light M of each light-emitting
element 7 reflected by the reflective/transmissive layer 43 in this
way advances through the filler material 44 towards the third lens
face 13 side, and subsequently enters the inner bottom surface 41c
of the prism placement recessing section 41. Then, the monitor
light M of each light-emitting element 7 that has entered the inner
bottom surface 41c advances through the lens array main body 34,
and is emitted from each third lens face 13 towards each
light-receiving element 8 corresponding with each third lens face
13.
[0127] On the other hand, the laser light La of each light-emitting
element 7 that has been transmitted by the reflective/transmissive
layer 43 enters the incident surface 42a of the prism 42
immediately after transmittance and advances towards the second
lens face 12 side on the optical path within the prism 42. In
addition, the light beam diameter of the laser light La increases
as the laser light La advances.
[0128] At this time, because the reflective/transmissive layer 43
is very thin, the refraction that occurs when the laser light La of
each light-emitting element 7 is transmitted through the
reflective/transmissive layer 43 is small enough to be ignored.
[0129] Next, the laser light La of each light-emitting element 7
that has advanced through the prism 42 is emitted outside of the
prism 42 from the outgoing surface 42b of the prism 42. The laser
light La passes through the filler material 44 and enters the right
inner surface 41b of the prism placement recessing section 41. At
this time, because the difference in refractive index among the
prism 42, the filler material 44, and the lens array main body 34
is small, as shown in FIG. 26, refraction and Fresnel reflection of
the laser light La of each light-emitting element 7 does not
occur.
[0130] Next, the laser light La of each light-emitting element 7
advances towards the second lens face 12 side on the optical path
within the lens array main body 34 subsequent to the right inner
surface 41b. In addition, the light beam diameter of the laser
light La increases as the laser light La advances.
[0131] After the laser light La of each light-emitting element 7 is
projected with a large spot diameter within the effective diameter
of each second lens face 12, the laser light La is then emitted
from each second lens face 12 towards the end face 5a of each
optical fiber 5.
[0132] According to the third embodiment, the effect foreign
matter/scratches on the second lens face 12 has on coupling
efficiency can be effectively reduced in a configuration suitable
for adjusting the output of the laser light La of the
light-emitting elements 7.
[0133] The variation examples applied to the first embodiment and
the second embodiment can also be applied accordingly to the third
embodiment.
Example 1
[0134] Next, in Example 1, simulation was conducted regarding the
effect foreign matter on the second lens face 12 has on coupling
efficiency between a VCSEL and optical fibers, while changing a
radius of curvature (center radius of curvature) R of the first
lens faces 11.
[0135] In the simulation, a type of lens array such as that
according to the first embodiment in which the second lens faces 12
are disposed behind the first lens faces 11 was used.
[0136] In addition, the VCSEL has .phi.0.01 mm, NA 0.15 (where the
light beam diameter is the diameter of a peripheral edge portion in
which the intensity decreases to 1/e.sup.2 of the maximum
intensity), and a usage wavelength of 850 nm. The optical fiber 5
has .phi.0.05 mm and NA 0.20.
[0137] Furthermore, the distance between the VCSEL and the first
lens faces 11 is 0.14 mm.
[0138] Still further, in the simulation, as shown in FIG. 27,
foreign matter that is .phi.0.02 mm in size is assumed to be
present in a position P.sub.1 (x=0.00 mm, y=0.015 mm) that is 0.015
mm from the center (x=0.00 mm, y=0.00 mm) of the second lens
12.
[0139] In addition, a defocus position on the optical fiber 5 side
is a position at which the coupling efficiency is optimal when no
foreign matter is present.
[0140] The results of the simulation conducted under the
above-described conditions are shown in Table 1, below, and FIG. 28
and FIG. 29.
TABLE-US-00001 TABLE 1 No foreign matter Foreign matter present
Coupling Trans- Coupling Trans- efficiency mission efficiency
mission R(mm) Beam shape (dB) factor (%) (dB) factor (%) 0.08
Collimated -0.52 88.7 -1.32 73.8 light 0.10 Spread -0.52 88.6 -1.15
76.8 converged light 0.12 Spread -0.54 88.4 -1.06 78.3 converged
light 0.14 Spread -0.52 88.6 -0.97 79.9 converged light
[0141] However, in FIG. 28, the horizontal axis indicates the
radius of curvature R of the first lens face 11. The vertical axis
indicates the coupling efficiency. In FIG. 29, the horizontal axis
indicates the radius of curvature R of the first lens face 11. The
vertical axis indicates the transmission factor.
[0142] As shown in Table 1, FIG. 28, and FIG. 29, when the radius
of curvature of the first lens face 11 is 0.08 mm, the light beam
obtained by the first lens face 11 is a collimated light that
departs from the scope of the present invention. The transmission
factor of the laser light La at the second lens face 12 and the
coupling efficiency of the laser light La with the optical fiber 5
are values that deteriorate the most during the simulation,
compared to when foreign matter is not present. A reason for this
is thought to be that, in the collimated light, the area occupancy
of foreign matter in relation to the light spot on the second lens
face 12 is high.
[0143] On the other hand, when the radius of curvature is 0.10 mm,
0.12 mm, or 0.14 mm, the light beam obtained by the first lens
surface 11 is a converged light that spreads wider than the
collimated light, or in other words, the light intended in the
present invention. The transmission factor of the laser light La at
the second lens face 12 and the coupling efficiency of the laser
light La with the optical fiber 5 are higher than those of the
collimated light (less deterioration in terms of comparison with
when foreign matter is not present). In particular, when the radius
of curvature is 0.14 mm, the transmission factor and the coupling
efficiency are the highest. A reason for this is thought to be
that, because a converged light that is spread wider than the
collimated light is obtained, the area occupancy of foreign matter
in relation to the light spot on the second lens face 12 can be
sufficiently reduced.
Example 2
[0144] Next, in Example 2, simulation similar to that in Example 1
was conducted on the type of lens array according to the second
embodiment that includes the reflective surface 23.
[0145] In the simulation, the distance between the VCSEL and the
first lens faces 11 is 0.28 mm.
[0146] In addition, in the simulation, as shown in FIG. 30, foreign
matter that is .phi.0.04 mm in size is assumed to be present in a
position P.sub.2 (x=0.00 mm, y=0.03 mm) that is 0.03 mm from the
center (x=0.00 mm, y=0.00 mm) of the second lens 12.
[0147] Other simulation conditions are similar to those in Example
1.
[0148] The results of the simulation are shown in Table 2, below,
and FIG. 31 and FIG. 32.
TABLE-US-00002 TABLE 2 No foreign matter Foreign matter present
Coupling Trans- Coupling Trans- efficiency mission efficiency
mission R(mm ) Beam shape (dB) factor (%) (dB) factor (%) 0.17
Collimated -0.53 88.5 -1.36 73.2 light 0.19 Spread -0.53 88.5 -1.29
74.3 converged light 0.21 Spread -0.53 88.5 -1.12 77.3 converged
light 0.23 Spread -0.54 88.3 -1.00 79.4 converged light
[0149] As shown in Table 2, FIG. 31, and FIG. 32, when the radius
of curvature of the first lens face 11 is 0.17 mm, the light beam
obtained by the first lens face 11 is a collimated light that
departs from the scope of the present invention. The transmission
factor of the laser light La at the second lens face 12 and the
coupling efficiency of the laser light La with the optical fiber 5
are values that deteriorate the most during the simulation.
[0150] On the other hand, when the radius of curvature is 0.19 mm,
0.21 mm, or 0.23 mm, the light beam obtained by the first lens
surface 11 is a converged light that spreads wider than the
collimated light, or in other words, the light intended in the
present invention. The transmission factor of the laser light La at
the second lens face 12 and the coupling efficiency of the laser
light La with the optical fiber 5 are higher than those of the
collimated light
[0151] Such tendencies are also likely to be similar when the lens
array according to the third embodiment is used.
[0152] The present invention is not limited to the above-described
embodiments. Various modifications can be made to an extent that
the features of the present invention are not compromised.
[0153] For example, the above-described embodiments are applied to
optical transmission as optical communication. However, the present
invention can also be effectively applied to optical reception.
When the present invention is applied to optical reception, a
configuration may be used in which light-receiving elements, such
as photodetectors, are disposed instead of the light-emitting
elements 7 in the positions of the light-emitting elements 7, and
laser light for reception is emitted from the end faces 5a of the
optical fibers 5 towards the second lens faces 12. In this
instance, the second lens faces 12 can be formed into convex lens
faces that converge the laser light emitted from the end faces 5a
of the optical fibers with a stronger refractive power than that
for collimation. As a result, even in optical reception, the light
spot diameter on the second lens face 12 can be made larger than
the light spot diameter on the first lens face 11, and the area
occupancy of foreign matter/scratches in relation to the light spot
on the second lens face can be reduced. Therefore, the effect
foreign matter/scratches have on coupling efficiency with the
light-receiving element can be reduced.
[0154] In addition, the present invention may be applied to optical
transmission bodies other than the optical fibers 5, such as an
optical waveguide.
EXPLANATIONS OF LETTERS OR NUMERALS
[0155] 1 sub-assembly [0156] 2 lens array [0157] 3 photoelectric
conversion device [0158] 5 optical fiber [0159] 7 light-emitting
element [0160] 11 first lens face [0161] 12 second lens face
* * * * *